U.S. Ser. No. 11/750,571, filed May 18, 2007, titled “Detachable Tag-Based Temperature Sensor For Use In Heating Of Food And Cookware,” assigned to the present assignee, is hereby incorporated by reference in its entirety into this patent application.
The present invention generally relates to devices used to heat the contents of cookware such as dishes, buffet trays and the like. More particularly, the invention relates to a heating device and system, such as for induction heating of objects such as cookware or food containers through stone or other materials on which cookware may be placed.
Various methods are known for heating cookware and food containers. As one example, radio-frequency identification (RFID) tagging systems have been used to activate and control magnetic induction heating systems for use in heating foods and associated food containers, cookware and warming/heat retention objects. Use of such systems allows objects not physically connected to a magnetic induction heater to be heated and temperature-regulated using RFID technology. In such systems, an RFID tag having a temperature sensor are mounted within the item to be heated, such as cookware; an RFID reader is located within the magnetic induction heater unit. When the tagged object comes within the reading field of the RFID reader, the tag may be used to transmit information such as temperature and the class of object being heated, so that the heater control circuitry may use the information to commence an appropriate heating cycle for heating and temperature-regulating the object. Various such systems are available, including those disclosed in U.S. Pat. Nos. 6,025,725 to Gershenfeld et al., and 6,320,169 and 6,953,919 to Clothier, the entire disclosures of each of these three patents hereby being incorporated by reference herein. Use of this technology enables relatively precise heating and temperature regulation.
Other non-contact/indirect, remote control methods are known or may be devised. As non-limiting examples, remote controller devices used with televisions typically operate based on optical (infrared) communication. Non-contact modes of communication other than RFID may be used, likewise, for measuring the temperature of cookware and food containers, such as those involving communication via optical means, ultrasound, infrared, or other communication modes.
Induction heating of cookware may be accomplished by mounting the cookware on a range or countertop. Often, it may be desirable to hide the induction heating unit beneath a countertop made of stone (e.g., granite, man-made composites such as silestone, etc.) or other materials (e.g., formica, glass, wood, etc.), which may be typically about 3 centimeters thick, as a rough exemplary range of thickness. The countertop carries the cookware, which may be induction-heated by conveyance of magnetic field waves passing through the stone. Due to its combustive nature, the use of wood may not be desirable. Stone and composites present problems in this application, as market experience and the inventors' own testing have shown that the substantial temperature variations involved in warming or heating of food containers or cookware tends to crack the stone or generate surface damage (mechanical and/or visual).
For warming food or liquid items held for serving, the U.S.D.A. sets 145° F. as a minimum holding temperature. Typically, because it is not desired to boil the food or liquid item, 180° F.-190° F. is the top range. The resulting temperature variations have proved problematic when using countertops made of stone or other materials due to cracking or surface damage issues.
Another problem encountered when using a stone, composite or other countertop covering an induction heating unit has been how to locate the cookware on the countertop so that it is properly positioned for heating activation within the radio tagging transmission area of the induction heating unit, as well as being optimally positioned for the induction heating process. Two factors complicate this problem. First, it may be desirable to have a “clean” countertop, devoid of markings, logos, designs, etc. Second, it may be desirable to have induction heater (e.g., buffet) units, for example, slidably mounted on tracks beneath the countertop, so that their location can change beneath the countertop. Accordingly, it would be advantageous to provide a way of indicating to the user when the cookware is properly located over the induction heating unit, and also to indicate whether the heating unit is currently heating the heat retention object.
Still another problem encountered in the industry of warming food items using cookware is how to control the temperature of the cookware remotely, using indirect heating.
It would also be advantageous to provide a cookware-warming device that may be used with any cookware, such that it need not be specially designed to have induction heating apparatus (e.g., an RFID tag) attached to it.
Accordingly, it would be advantageous to provide a cookware heating device and system that solves the problems recited above, while providing new advantages not currently available.